This invention relates to a device for producing ceramic mouldings.
In German Patent Specification No. 3,101,236 there is disclosed a device for producing ceramic mouldings comprising two half-moulds which are adjustable between a relatively open position and a relatively closed position by means of two parts of an adjusting device, especially a press, these two parts being movable in relation to each other, and these two parts defining between them a mould cavity which is closed in the relatively closed position, the mould cavity having at least one inlet opening for particulate, ceramic moulding compositions, at least one extraction orifice and possibly a fluidizing air inflow opening, cooperating sealing surfaces being provided on sealing surface carriers of the mould halves which are movable in relation to each other, said sealing surfaces coming together during the closing motion of the adjusting device, separating during the opening movement of the adjusting device and sealing the mould cavity in the relatively closed position.
In the device of German Patent Specification No. 3,101,236, a vacuum is created in the closed mould cavity to draw in the particulate ceramic moulding composition. The particulate ceramic composition is sucked into the mould cavity by this vacuum, its distribution in the mould chamber being assisted by the introduction of fluidizing air into the moulding composition at the point where it enters the mould cavity or at a nearby point. In German Patent Specification No. 3,101,236 a procedure is disclosed in which the impact velocity of the moulding composition particles sucked in against the extraction orifices at the start of the suction process is kept low by a set of filters formed as part of the mouldings at the extraction orifices. This set of filters allows the further extraction of air by preventing obstruction of these extraction orifices by too densely packed moulding composition particles which may also have been destroyed on impact. By means of the process according to German Patent Specification No. 3,101,236 it was possible for the first time to achieve by suction a satisfactory filling of the mould cavity with a moulding composition and furthermore to precompress the moulding composition in the mould cavity during suction to such an extent that certain manipulations are possible without the pre-moulding being damaged. In particular, it has proved possible to replace the injection head, by means of which a vacuum is first created and then the moulding composition and possibly the fluidizing air are supplied, by a pressing head, without any large-scale destruction of the pre-moulding occurring during the replacement of the injection head by the pressing head. Nevertheless the pre-moulding has randomly yet repeatedly shown signs of damage caused when the injection head is removed, a fact which has not hitherto been explicable.
It has now been discovered that a considerable reduction in damage caused to the pre-moulding when the injection head is removed can be achieved by a relatively simple measure.
This relatively simple measure consists, for a device as described, in providing a spring suspension system between at least a part of the adjusting device and the sealing surface carrier of the corresponding mould half. This spring system is stressed during the closing motion of the adjusting device and relaxes during the opening movement of the adjusting device.